실버1
문제 1991
해당 문제 링크

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정답
딕셔너리 사용, 재귀
n=int(input())
tree={}
for _ in range(n):
root, left, right = input().split()
tree[root] = [left, right]
def preorder(root):
if root!= '.':
print(root, end='')
preorder(tree[root][0])
preorder(tree[root][1])
def inorder(root):
if root!= '.':
inorder(tree[root][0])
print(root, end='')
inorder(tree[root][1])
def postorder(root):
if root!= '.':
postorder(tree[root][0])
postorder(tree[root][1])
print(root, end='')
preorder('A')
print()
inorder('A')
print()
postorder('A')